Australian influenza report 2011 - 25 June - 8 July 2011 (#8/11)

The Australian Influenza Report is compiled from a number of data sources, including laboratory-confirmed notifications to NNDSS, sentinel influenza-like illness reporting from general practitioners and emergency departments, workplace absenteeism, and laboratory testing. A more in-depth annual report is also published in Communicable Diseases Intelligence.

hospitalisations, ICU admissions and deaths from sentinel systems; and

clinical severity in hospitalised cases and ICU admissions.

Is the virus changing?

Indicated by trends in:

drug resistance; and

genetic drift or shift from laboratory surveillance.

Summary

Levels of influenza-like illness (ILI) in the community continued to increase through both sentinel general practitioner surveillance systems and ILI presentations to emergency departments.

Notifications have continued to rise nationally, with increases most notable in South Australia, Queensland and New South Wales.

During this reporting period there were 1,555 laboratory confirmed notifications of influenza, with Queensland reporting the highest number of notifications, followed by New South Wales and South Australia. The majority of virus detections have been pandemic (H1N1) 2009, with co-circulation of influenza B.

Influenza B in South Australia has continued to represent the majority of their notifications (80%), and also accounted for over half of all influenza B reported nationally over this period. Queensland and New South Wales have reported mostly pandemic (H1N1) 2009 with some co-circulation of influenza B.

As at 8 July 2011, there have been 7,488 confirmed cases of influenza reported to the National Notifiable Diseases Surveillance System (NNDSS) in 2011, compared with 1,294 for the same period in 2010.

The WHO has reported that influenza activity in the temperate countries of the northern hemisphere is at baseline inter-seasonal level. Influenza activity in the temperate countries of the southern hemisphere has increased in recent weeks.

1. Influenza activity in Australia

Influenza-Like Illness

Sentinel General Practice Surveillance

Sentinel general practitioner ILI consultation rates continued to increase this fortnight. In the week ending 3 July 2011, the national ILI consultation rate to sentinel GPs was 14 cases per 1,000 consultations, up from 11 cases per 1,000 consultations last fortnight (Figure 1).

Figure 1. Weekly rate of ILI reported from GP ILI surveillance systems from 1 January 2008 to 19 June 2011*

* Delays in the reporting of data may cause data to change retrospectively. As data from the VIDRL surveillance system is combined with ASPREN data for 2010 and 2011, rates may not be directly comparable across 2008 and 2009.
SOURCE: ASPREN and VIDRL GP surveillance system1

Of the ASPREN ILI specimens collected in the fortnight ending 19 June 2011, 3 specimens (6%) were positive for influenza, with all of those being typed as influenza type B. Due to the small number of specimens tested it is difficult to yet determine any general trends in influenza positivity. Seven specimens were positive for other respiratory viruses, with the majority of these being rhinovirus (4) (Table 1). Please note, there was no additional ASPREN ILI swab testing data available for this reporting period.

Table 1. ASPREN ILI consultations laboratory respiratory viral tests that were positive for influenza or other respiratory virus, 1 January 2011 to 19 June 2011.

ASPREN Fortnight
(6 June – 19 June 2011)

ASPREN YTD
(1 Jan – 19 June 2011)

Total specimens tested

47

389

Total Influenza Positive

3

48

Influenza A

0

35

Pandemic (H1N1) 2009

0

24

Seasonal A/H3N2

0

1

Influenza A untyped

0

10

Influenza B

3

13

Total Positive other Resp. Viruses*

7

107

* Other respiratory viruses include RSV, para-influenza, adenovirus and rhinovirus.

Western Australia Emergency Departments

In the fortnight ending 10 July 2011 there continued to be an increase in the number of respiratory viral presentations to WA EDs. Over this period there were 1,064 presentations, including 58 admissions (Figure 2). The proportion of presentations admitted to hospital remains stable.

Figure 2. Number of respiratory viral presentations to WA EDs from 1 January 2008 to 10 July 2011, by week

New South Wales Emergency Departments

In the week ending 8 July 2011 the rate of ILI presentations to NSW EDs was 2.5 cases per 1,000 consultations (Figure 3). This is slightly higher than the previous week’s rate (2.1 per 1,000 consultations), but is within the usual range for this time of year. A higher proportion of presentations were reported among people aged 15 to 44 years (69%).3

Figure 3. Rate of influenza-like illness presentations to NSW Emergency Departments between May and October, 2008 to 2011, by week

FluTracking

FluTracking, a national online system for collecting data on ILI in the community, reported that in the week ending 10 July 2011 fever and cough was reported by 2.9% of vaccinated participants and 3.6% of unvaccinated participants (Figure 4)4. Fever, cough and absence from normal duties was reported by 1.5% of vaccinated participants and 1.4% of unvaccinated participants.

Up to 10 July 2011, 6,722 out of 10,237 (65.7%) participants reported having received the seasonal vaccine so far. Of the 2,405 participants who identified as working face-to-face with patients, 1,919 (79.8%) have received the vaccine.

Figure 4. Rate of ILI symptoms among Flutracking participants by week, from week ending 8 May 2011 to week ending 10 July 2011.

Source: FluTracking

National Health Call Centre Network

The number of ILI-related calls to the National Health Call Centre Network (NHCCN) continued to increase during this fortnight compared to recent weeks. The percentage of total calls also continued to increase. In the week ending 10 July 2011, 10% of calls to the NHCCN were ILI related, which is slightly above the same period in 2010 (Figure 5).

Figure 5. Number of calls to the NHCCN related to ILI and percentage of total calls, Australia, 1 January 2010 to 10 July 2011

Note: National data do not include QLD and VIC
Source: NHCCN data

Laboratory Confirmed Influenza

Laboratory Confirmed Cases Notified to Health Departments

During this reporting period there were 1,555 laboratory confirmed influenza notifications reported to the NNDSS. Of these notifications, there were 656 in Qld, 391 in NSW, 371 in SA, 62 in Vic, 36 in WA, 24 in the ACT, 14 in TAS, and 1 in the NT (Figure 6). A weekly breakdown of trends by state and territory highlights that in recent weeks notifications have continued to increase mostly in South Australia, Queensland and New South Wales (Figure 8).

Figure 6. Laboratory confirmed cases of influenza in Australia, 1 January to 8 July 2011, by state, by week.

Up to 8 July, there have been 7,448 laboratory confirmed notifications of influenza diagnosed during 2011 (Figure 7). Of these notifications, there have been 3,228 notified in Qld, 1,417 in NSW, 1,302 in SA, 683 in Vic, 341 in the NT, 311 cases in WA, 96 cases in Tas and 70 cases in the ACT. All jurisdictions reported higher than usual numbers of notifications over the summer months, especially in the Northern Territory and Queensland. The reason for this unusually high activity earlier in the year is not clear, but it does not appear to be due solely to increased testing.

Figure 7. Laboratory confirmed cases of influenza in Australia, 1 January 2005 to 8 July 2011

Source: NNDSS

Figure 8. State breakdowns of laboratory confirmed cases of influenza, 1 January to 8 July 2011, by week

Source: NNDSS

Of the 1,555 influenza notifications reported to the NNDSS this reporting period, 529 were influenza A (untyped), 498 were pandemic (H1N1) 2009, 520 were influenza B, 4 were A/H3N2, 3 were untyped and one notification was reported as influenza type A&B (Figure 9). Compared to the beginning of the year, there appears to be very little A/H3N2 circulating.

Influenza B in South Australia has continued to represent the majority of their notifications (80%), and also accounted for over half of all influenza B reported nationally over this period. Queensland and New South Wales have reported mostly pandemic (H1N1) 2009 with some co-circulation of influenza B. Note: South Australian and Queensland testing data are not reflected in the sentinel laboratory data.

So far in 2011, 2,962 (40%) cases have been sub-typed as influenza A (untyped), 1,969 (26%) as pandemic (H1N1) 2009, 621 (8%) as type A/H3N2, and 37 (<1%) were type A&B. A further 1,827 (25%) have been characterised as influenza type B and 32 (<1%) were untyped (Figure 9).

Note: Northern Territory sub-typing results reported to the NNDSS as "Influenza A/Not Pandemic" have been counted as influenza A/H3N2 notifications.

Figure 9. Laboratory confirmed cases of influenza in Australia, 1 January 2011 to 8 July 2011, by sub-type and week

Source: NNDSS

Sentinel Laboratory Surveillance

Results from sentinel laboratory surveillance systems for this reporting period show that 6.3% (62/988) of the respiratory tests conducted over this period were positive for influenza (Table 2). Positive influenza specimens were reported from all sentinel laboratories, except the Northern Territory. Please note, sentinel laboratory surveillance data were not available from Tasmania this reporting period.

Table 2. Laboratory respiratory tests that tested positive for influenza, 25 June to 8 July 2011

NSW NIC

WA NIC

NT
(Reported by WA NIC)

VIC NIC

TAS
Laboratories

Total specimens tested

463

325

3

197

-

Total Influenza Positive

32

17

0

13

-

Positive Influenza A

20

15

0

8

-

Pandemic (H1N1) 2009

11

10

0

5

-

A/H3N2

1

5

0

1

-

Influenza A untyped

8

0

0

2

-

Positive Influenza B

12

2

0

5

-

The most common respiratory virus detected

RSV

RSV

-

Picornavirus

-

In 2011 a total of 4.2% of specimens have been positive for influenza. A breakdown of subtypes within this positive proportion by fortnight is highlighted in Figure 10.

Figure 10. Proportion of sentinel laboratory* tests positive for influenza, by subtype and fortnight, 30 April to 8 July 2011.

* Currently excludes Tasmanian sentinel surveillance data

Influenza Hospitalisations

Influenza Complications Alert Network (FluCAN) - Victoria

The Victorian Influenza Complications Alert Network (FluCAN) sentinel hospital system has reported 5 hospitalisations, including one death, associated with influenza since 1 May 2011. Three of the patients were admitted with influenza A (untyped) infection and two were admitted with influenza type B infection. The majority of these patients were reported as having underlying co-morbidities.

Figure 11. Number of influenza hospitalisations at sentinel hospitals, Victoria, by week, 1 May to 7 July 2011

Australian Paediatric Surveillance

The Australian Paediatric Surveillance Unit (APSU) conducts seasonal surveillance of children aged 15 years and under who are hospitalised with severe complications of influenza. Details of admissions are reported on a weekly basis to the Department.

For the week ending 7 July 2011, there were 6 hospitalisations associated with severe influenza complications in children, including one ICU admission. The majority of these hospitalisations were associated with pandemic (H1N1) 2009 infection.

Deaths associated with influenza and pneumonia

Nationally Notified Influenza Associated Deaths

In 2011, 5 influenza associated deaths have been notified to the NNDSS, with all cases having pandemic (H1N1) 2009.

New South Wales Influenza and Pneumonia Death Registrations

Death registration data up to 17 June 2011 showed that there were 1.1 pneumonia or influenza associated deaths per 100,000 population in NSW, which is below the seasonal threshold of 1.7 per 100,000 NSW population for this period (Figure 12).3
[Figure 12. Rate of deaths classified as influenza and pneumonia from the NSW Registered Death Certificates, 2006 to 17 June 2011

2. Virology

Typing and antigenic characterisation

WHO Collaborating Centre for Reference & Research on Influenza (WHO CC) in Melbourne

From 1 January to 10 July 2011, there were 673 Australian influenza isolates subtyped by the WHO CC with the majority of these isolates subtyped as pandemic (H1N1) 2009 (46%) (Table 3).

Table 3. Typing of influenza isolates from the WHO Collaborating Centre, from 1 January 2011 to 10 July 2011

Type/Subtype

ACT

NSW

NT

QLD

SA

TAS

VIC

WA

TOTAL

Pandemic (H1N1) 2009

0

41

28

177

3

16

24

22

311

A(H3N2)

0

3

48

105

1

2

5

8

172

B

0

12

32

32

91

2

17

4

190

Total

0

56

108

314

95

20

46

34

673

SOURCE: WHO CC
Please note: There may be up to a month delay on reporting of samples.
Isolates tested by the WHO CC are not necessarily a random sample of all those in the community.

Antigenic characterisation has shown influenza isolates to be a close match with the composition of the 2011 southern hemisphere influenza vaccine with some viruses showing reduced reactivity, however there has been insufficient testing to date to determine any general trends.

Antiviral Resistance

The WHO Collaborating Centre in Melbourne has reported that from 1 January 2011 to 10 July 2011, one isolate (out of 925 tested) has shown resistance to oseltamivir by enzyme inhibition assay (EIA). A further isolate, out of a total of 7 pandemic H1N1 (2009) tested by pyrosequencing, has shown the H275Y mutation known to confer resistance to oseltamivir.

3. International Influenza Surveillance

The WHO5 has reported that as at 1 July 2011 influenza activity in the temperate countries of the northern hemisphere are at baseline inter-seasonal levels. Transmission in tropical arrears is low overall, with focal areas of transmission noted in a few countries of Central America and northern South America, western and eastern regions of sub-Saharan Africa, and tropical Asia. South Africa has continued to report increasing numbers of both mild and severe cases, primarily related to pandemic (H1N1) 2009.

National Influenza Centres in 71 countries have reported that for the period 5 June to 18 June 2011, a total of 837 specimens were reported as positive for influenza viruses, 583 (69.7%) were typed as influenza A and 254 (30.3%) as influenza B. Of the sub-typed influenza A viruses reported, 83.2% were pandemic (H1N1)2009 and 16.7% were influenza A(H3N2) 6.

WHO have released a summary review of the northern hemisphere winter influenza season7. The summary review notes that the most commonly detected virus was different in North America, where influenza A(H3N2) and influenza type B co-circulated with pandemic (H1N1)2009, and Europe, where influenza A(H1N1)2009 was by far the most commonly detected virus. Although it was no longer the predominant influenza virus circulating in many parts of the world, pandemic (H1N1) 2009 otherwise behaved much the same way as it had during the pandemic in terms of the age groups most affected and the clinical pattern of illness. More than 90% of viruses detected around the world during the northern hemisphere influenza season were similar antigenically to those found in the seasonal trivalent influenza vaccine. Antiviral resistance in pandemic (H1N1)2009 remained at a very low level.

The WHO has released their recommendation for the antigen composition of 2011-2012 northern hemisphere influenza season trivalent flu vaccine8 It is recommended that vaccines contain the following:

an A/California/7/2009 (H1N1)-like virus;

an A/Perth/16/2009 (H3N2)-like virus;

a B/Brisbane/60/2008-like virus.

This recommended composition is the same as the 2010-2011 Northern Hemisphere and the 2011 Southern Hemisphere vaccine compositions.

4. Data considerations

The information in this report is reliant on the surveillance sources available to the Department of Health and Ageing. As access to sources increase as the season progresses, this report will be updated with the additional information.

This report aims to increase awareness of pandemic (H1N1) 2009 and seasonal influenza in Australia by providing an analysis of the various surveillance data sources throughout Australia. While every care has been taken in preparing this report, the Commonwealth does not accept liability for any injury or loss or damage arising from the use of, or reliance upon, the content of the report. Delays in the reporting of data may cause data to change retrospectively. For further details about information contained in this report please contact the Influenza Surveillance Team through flu@health.gov.au.

Sentinel General Practice Surveillance

The Australian Sentinel Practices Research Network (ASPREN) has Sentinel GPs who report ILI presentation rates in NSW, NT, SA, ACT, VIC, QLD, TAS and WA. As jurisdictions joined ASPREN at different times and the number of GPs reporting has changed over time, the representativeness of ASPREN data in 2011 may be different from that of previous years. ASPREN data and VIDRL influenza surveillance data are sent to the Department on a weekly basis. Approximately 30% of all ILI patients presenting to ASPREN sentinel GPs are swabbed for laboratory testing. Please note the results of ASPREN ILI laboratory respiratory viral tests now include Western Australia.

Sentinel Emergency Department Data

WA - ED surveillance data are extracted from the ‘Virus Watch’ Report. This report is provided weekly. The Western Australia Influenza Surveillance Program collects data from eight Perth EDs.

NSW - ED surveillance data are extracted from the ‘Weekly Influenza Report, NSW’. The New South Wales Influenza Surveillance Program collects data from 56 EDs across New South Wales.

FluTracking

FluTracking is a project of the University of Newcastle, the Hunter New England Area Health Service and the Hunter Medical Research Institute. FluTracking is an online health surveillance system to detect epidemics of influenza. It involves participants from around Australia completing a simple online weekly survey, which collects data on the rate of ILI symptoms in communities.

Sentinel Laboratory Surveillance data

Influenza Complications Alert Network (FluCAN)

The Victorian Influenza Complications Alert Network (FluCAN) sentinel hospital system monitors influenza hospitalisations at the following sites throughout Victoria: Geelong, Royal Melbourne, Monash and Alfred.

Australian Paediatric Surveillance Unit

The Australian Paediatric Surveillance Unit (APSU) conducts seasonal surveillance of children aged 15 years and under who are hospitalised with severe complications of influenza. Reports are collated on a weekly basis from approximately 1,300 paediatricians and other child health clinicians around Australia. The protocol and case definition is available at: http://www.apsu.org.au/download.cfm?DownloadFile=96DE7B48-0CC2-E99A-525BCD4BD6A2CB80.

WHO Collaborating Centre for Reference & Research on Influenza (WHO CC)

Data are provided weekly to the Communicable Disease and Surveillance Branch from the WHO CC.

Deaths associated with influenza and pneumonia

Nationally reported influenza associated deaths are notified by jurisdictions to the NNDSS which is maintained by the Department of Health and Ageing. However these are an underestimation of the true number of deaths occurring in the community associated with influenza.

NSW influenza and pneumonia deaths data are collected from the NSW Registry of Births, Deaths and Marriages. Figure 6 is extracted from the ‘Weekly Influenza Report, NSW’.